For many years protective garments have been worn by people for the purpose of protection from a harsh or dangerous environment. One example of such a protective garment is a firefighter's turnout coat. While these protective garments have become proficient at insulating the wearer from the potentially hazardous environment, such garments have also reduced the wearer's ability to sense changing conditions of the environment. In the past, firefighters detected extreme temperatures with their earlobes, which were the only part of the body exposed to the atmosphere. Unfortunately, the protective clothing now required to be worn by firemen including turnout coats, hoods, helmets, and boots, cover the entire body, leaving no bodily means of detecting extreme temperatures.
To help reduce the risk of severe bums, U.S. Pat. No. 3,201,771 discloses a firefighters' helmet having a plurality of thermostatic elements distributed about the helmet. The thermostatic elements are connected to an electrical circuit and the elements cause the electrical circuit to sound a warning horn in a dangerous heat environment. The patent also discloses that the warning system of the helmet may be activated manually in a situation where the firefighter becomes disoriented in a burning structure. The drawback of such a firefighter's helmet is that the thermostatic elements and electrical circuit including the power supply are mounted on the exterior of the helmet. This location makes the helmet heavy and awkward to wear. This location also exposes the electrical circuit to the same high ambient and radiant temperatures as the sensors, thus creating a greater likelihood of electronic failure than if it were located in an insulated environment. The location of the electrical circuit also subjects the circuit to a greater risk of failure caused by debris falling on the helmet. In addition, such a temperature sensing device does not detect radiant heat. U.S. Pat. No. 4,914,422 discloses a personal alert safety system (PASS) which attaches to a firefighter's shoulder harness. The system audibly indicates temperature changes in 100.degree. F. increments within a hazardous environment. The system also includes a motion sensor which audibly indicates lack of motion after a period of time. Because the system is mounted externally on a firefighter's shoulder strap, the electronics of the unit are exposed to the same high ambient and radiant temperatures as the electronics of the helmet warning system described above. Also, the external location of the electronic unit increases the risk of electronic component damage of failure caused by falling debris, or can snag on an obstruction where it can be damaged, and/or compromise the firefighter's movement.
The present invention greatly improves the reliability of prior art warning systems by incorporating a thermal warning circuit within a protective garment such as a firefighters' turnout coat. The system provides the garment wearer with a reliable audible alarm when dangerous high temperature conditions exist such as when ambient and radiant heat from a burning structure are conducive to flashover (where the entire room suddenly ignites) or where such excessive radiant heat can cause the temperature of the firefighter's protective clothing to increase so as to cause it to disintegrate, potentially placing firefighters at risk of death or receiving severe burns.